From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f42.google.com (mail-pa0-f42.google.com [209.85.220.42]) by kanga.kvack.org (Postfix) with ESMTP id CCF346B0038 for ; Mon, 16 Mar 2015 22:04:01 -0400 (EDT) Received: by pabyw6 with SMTP id yw6so82243904pab.2 for ; Mon, 16 Mar 2015 19:04:01 -0700 (PDT) Received: from lgemrelse7q.lge.com (LGEMRELSE7Q.lge.com. [156.147.1.151]) by mx.google.com with ESMTP id nt3si26009938pdb.180.2015.03.16.19.03.59 for ; Mon, 16 Mar 2015 19:04:01 -0700 (PDT) Date: Tue, 17 Mar 2015 11:04:02 +0900 From: Joonsoo Kim Subject: Re: [PATCH v4 0/5] mm: cma: add some debug information for CMA Message-ID: <20150317020401.GC19483@js1304-P5Q-DELUXE> References: <20150317014306.GB19483@js1304-P5Q-DELUXE> <5507894A.2080008@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5507894A.2080008@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: Stefan Strogin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Marek Szyprowski , Michal Nazarewicz , aneesh.kumar@linux.vnet.ibm.com, Laurent Pinchart , Dmitry Safonov , Pintu Kumar , Weijie Yang , Laura Abbott , SeongJae Park , Hui Zhu , Minchan Kim , Dyasly Sergey , Vyacheslav Tyrtov , Aleksei Mateosian , gregory.0xf0@gmail.com, gioh.kim@lge.com, pavel@ucw.cz, stefan.strogin@gmail.com On Mon, Mar 16, 2015 at 09:54:18PM -0400, Sasha Levin wrote: > On 03/16/2015 09:43 PM, Joonsoo Kim wrote: > > On Mon, Mar 16, 2015 at 07:06:55PM +0300, Stefan Strogin wrote: > >> > Hi all. > >> > > >> > Here is the fourth version of a patch set that adds some debugging facility for > >> > CMA. > >> > > >> > This patch set is based on next-20150316. > >> > It is also available on git: > >> > git://github.com/stefanstrogin/linux -b cmainfo-v4 > >> > > >> > We want an interface to see a list of currently allocated CMA buffers and some > >> > useful information about them (like /proc/vmallocinfo but for physically > >> > contiguous buffers allocated with CMA). > >> > > >> > For example. We want a big (megabytes) CMA buffer to be allocated in runtime > >> > in default CMA region. If someone already uses CMA then the big allocation > >> > could fail. If it happened then with such an interface we could find who used > >> > CMA at the moment of failure, who caused fragmentation and so on. Ftrace also > >> > would be helpful here, but with ftrace we can see the whole history of > >> > allocations and releases, whereas with this patch set we can see a snapshot of > >> > CMA region with actual information about its allocations. > > Hello, > > > > Hmm... I still don't think that this is really helpful to find root > > cause of fragmentation. Think about following example. > > > > Assume 1024 MB CMA region. > > > > 128 MB allocation * 4 > > 1 MB allocation > > 128 MB allocation > > 128 MB release * 4 (first 4) > > try 512 MB allocation > > > > With above sequences, fragmentation happens and 512 MB allocation would > > be failed. We can get information about 1 MB allocation and 128 MB one > > from the buffer list as you suggested, but, fragmentation are related > > to whole sequence of allocation/free history, not snapshot of allocation. > > This is solvable by dumping task->comm in the tracepoint patch (1/5), right? Yes, it can be solved by 1/5. I mean that I'm not sure patch 4/5 is really needed or not. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org